It makes more sense to tell him what happened, if only for the chance that it might change things.

[ That's really all they can do with the information and options they have. He doesn't anticipate it will lead to a bad outcome if they tell him. It would be the logical thing to do.

However ... he wouldn't be himself, if all he is, is logical. ]

But he's calm and happy here so far. [ That will ruin everything. ]